You can customize everything about Sublime Text: the color scheme, text font, the global key bindings, the tab stops, the file-specific key bindings and snippets, and even the syntax highlighting rules. Preferences are encoded as JSON files. Language-specific definitions are XML preferences files. There is an active community around Sublime Text that creates and maintains Sublime Text packages and plug-ins. Many features that I initially thought Sublime Text lacked — including JSLint and JSHint interfaces, JsFormat, JsMinify, PrettyJSON, and Git support — turn out to be available through the community, using the Package Installer.
One of the reasons for Sublime Text's great performance is that it is tightly coded. Another reason is that Sublime Text is not an IDE, and it doesn't need the bookkeeping overhead of an IDE.
From a developer's viewpoint, this is a tricky trade-off. If you're in a tight, test-driven, "red, green, refactor" development loop, then an IDE that is set up to edit, test, refactor, and track code coverage will help you the most. If you're doing code reviews or major edits, on the other hand, you'll want the fastest, most efficient editor you can find, and that editor might well be Sublime Text.
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